1. Field of the Invention
The present invention relates to a system for accommodating a sitting attitude of a vehicle occupant. More particularly, the present invention relates to a system for securing a comfortable sitting attitude of a vehicle occupant by adjusting the sitting attitude in correspondence with an inertial force acting on a vehicle occupant during the running of a vehicle, or by adjusting the sitting attitude such that the occupant can hold with a comfortable posture the inertial force acting during the running of a vehicle.
2. Description of the Related Art
Conventionally, a vehicle is provided with seats for occupants to be seated in, and these seats are fixed to a vehicle body so that they do not move when the vehicle is running. Recently, high-speed running has become possible in conjunction with the improved performance of the vehicles, and maneuvering stability has improved substantially. With respect to vehicle seats, it has become possible to adjust their positions in conformity with the physique of the occupant, and improvements have been made in terms of the occupants' feeling of being seated in the seat. However, since the seats do not move during running, depending on a running condition of the vehicle, e.g., when the vehicle turns, an inertial force (centrifugal force) occurring during a turn has caused a slippage in the seated condition of the occupant, thereby imparting an uncomfortable feeling to the occupant. To overcome this problem, vehicle seats have been proposed in which the inertial force is detected by a sensor (an acceleration sensor, a vehicle speed sensor, a revolution sensor, or the like) during the running of the vehicle, and the seated condition of the occupant is adjusted by moving the seat on the basis of a detected value thereof, thereby to overcome the uncomfortable feeling (Japanese Patent Application Laid-Open No. 84232/1982 and Japanese Utility Model Application Laid-Open No. 97040/1983). These prior art techniques attempt to constantly maintain a comfortable seated condition by moving the seat in a transverse direction (i.e., in a direction perpendicular to the traveling direction of the vehicle, hereafter the same) by following a movement of the vehicle, e.g., the movement of the vehicle during a turn. In addition, there is another technique in which the posture of the seat is changed in the transverse direction by detecting the height of the vehicle (Japanese Utility Model Application Laid-Open No. 237/1991). Thus, the posture of the seat has hitherto been moved only in the transverse direction.
In the vehicle, however, a force acts on the suspension and the like in correspondence with the inertial force, with the result that the posture of the vehicle body changes. For this reason, even if the position of the seat is controlled in the transverse direction on the basis of the inertial force determined from the vehicle speed, the turning direction of the vehicle, and the like in the conventional manner, since a change in the posture of the vehicle occurs, there has been the problem that the seat cannot be controlled in conjunction with a change in the posture of the vehicle and to an optimum postural position suited to driving.
In addition, when the occupant moves passively after getting in the vehicle or the like, since there are cases where information obtained from the space sense, e.g., the sense of equilibrium, the visual sense, the positional sense, and the like, differs from information stored in the brain, so that the occupant can lapse into a condition inconsistent with a condition that can be estimated on the basis of his or her past experience stored in the brain. Hence, it is known that some drivers become carsick for the above-described reason.
Accordingly, even if the posture of the seat is controlled in correspondence with the running condition of the vehicle, there are cases where the information stored in the occupant's brain does not accord with the space sense resulting from the control of the posture of the seat, thereby possibly causing discomfort such as carsickness. Whether or not the discomfort such as carsickness occurs depends on the occupant (individual). If the posture of the seat is only controlled univocally in conjunction with a change in the posture of the vehicle, it is difficult to secure optimum postures for all the occupants, and such a measure does not overcome the discomfort of all the occupants.
Furthermore, when the running condition of the vehicle is maintained at the time of changing a lane during high-speed running or at the time of running on a rough road, a winding road, or the like, the angular velocity of the steering wheel is large, and the steering wheel is turned back clockwise or counterclockwise within a short period of time. In such a case, the movement of the vehicle does not coincide with the rotational angle of the steering wheel. Hence, even if the control of the seat posture is effected in correspondence with the rotational angle of the steering wheel, or in correspondence with the movement of the vehicle, the driver can possibly feel discomfort.
Moreover, at the time of starting (accelerating), braking (decelerating), changing a lane during high-speed running, and turning on a rough road, the direction of the inertial force changes substantially during a short period of time, so that the posture of the vehicle changes substantially in both the longitudinal and transverse directions of the vehicle. For this reason, it is necessary to effect control within a short period of time. In addition, if the control of the seat posture is effected with respect to the transverse direction only, a postural displacement in the longitudinal direction remains in the occupant. Hence, it is difficult to secure an optimum posture during driving, so that such a measure does not overcome the discomfort of the occupant.